|  | 4.2 | Layer 1 Design
| 4.3.1 |
Designing the layer 1 topology: signaling method, medium type, and maximum length
In this section, you will examine Layer 1 star and extended star topologies. The physical cabling is one of the most important components to consider when designing a network. Design issues include the type of cabling to be used (typically copper or fiber) and the overall structure of the cabling. Layer 1 cabling media include types such as Category 5 unshielded twisted-pair (UTP) and fiber-optic cable, along with the TIA/EIA-568-A standard for layout and connection of wiring schemes. In addition to distance limitations, you should carefully evaluate the strengths and weaknesses of various topologies, as a network is only as effective as its underlying cable. Most network problems are caused by Layer 1 issues. If you are planning any significant changes for a network, you should do a complete cable audit to identify areas that require upgrades and rewiring. Whether you are designing a new network or recabling an existing one, fiber-optic cable should be used in the backbone and risers, with Category 5 UTP cable in the horizontal runs. The cable upgrade should take priority over any other needed changes, and enterprises should ensure-without exception-that these systems conform to well-defined industry standards, such as the TIA/EIA-568-A specifications. The TIA/EIA-568-A standard specifies that every device connected to the network should be linked to a central location with horizontal cabling. This is true if all the hosts that need to access the network are within the 100-meter distance limitation for Category 5 UTP Ethernet, as specified by TIA/EIA-568-A standards. The table in figure lists cable types and their characteristics. Upcoming Changes in Cabling Standards
| Threaded Case Study
Washington Project: Speed and Expansion

For the Washington School District network, you need to build the Layer 1 components of the district network with speed and expansion capabilities. As you know, the physical layer controls the way data is transmitted between the source and a destination node. Therefore, the type of media and topology you select helps you determine how much data can travel across the network and how quickly.

| Web Links
| Spurgeon's Ethernet Site
| Gigabit Ethernet